1. Technical Field
The present invention relates to a quantum interference device, an atomic oscillator, an electronic apparatus, and a moving object.
2. Related Art
As an oscillator having long-term accurate oscillation characteristics, there has been known an atomic oscillator, which oscillates based on the energy transition of an atom of alkali metal such as rubidium or cesium.
In general, the operation principles of atomic oscillators are roughly classified into a system using a double resonance phenomenon due to light and microwave, and a system using the quantum interference effect (coherent population trapping (CPT)) due to two types of light different in wavelength from each other. The atomic oscillator using the quantum interference effect can be miniaturized to a size smaller than the atomic oscillator using the double resonance phenomenon, and is therefore expected to be mounted on a variety of types of apparatuses in recent years (see, e.g., JP-A-2014-17824 (Document 1)).
As is disclosed in, for example, Document 1, the atomic oscillator using the quantum interference effect is provided with a gas cell having gaseous alkali metal encapsulated therein, a light source for emitting a resonance light pair for resonating the alkali metal in the gas cell, and alight detector (alight receiving section) for detecting the resonance light pair having been transmitted through the gas cell. Further, in such an atomic oscillator, there occurs an electromagnetically induced transparency (EIT) phenomenon in which both of the two types of resonance light are transmitted without being absorbed by the alkali metal in the gas cell in the case in which the difference in frequency between the two types of resonance light is a specific value, and an EIT signal, which is a rapid signal generated due to the EIT phenomenon, is detected with the light detector, and the EIT signal is used as a reference signal.
Here, from a viewpoint of enhancing the short-term frequency stability, the EIT signal is preferably small in linewidth (half bandwidth) and high in strength. Therefore, for example, in the atomic oscillator related to Document 1, there is used the circularly polarized resonance light pair for the purpose of enhancing the strength of the EIT signal.
However, in the atomic oscillator related to Document 1, since the alkali metal in the gas cell is irradiated only with the resonance light pair circularly polarized in the same direction, there occurs bias in the distribution of the magnetic quantum number of the alkali metal. Therefore, the number of the metal atoms having a desired magnetic quantum number making a contribution to the EIT decreases, and as a result, the strength of the EIT signal cannot sufficiently be increased.